1. Field
Apparatuses and methods consistent with exemplary embodiments relate to an image projection apparatus, and more specifically, to a focus adjustment device for use in a portable image projection apparatus.
2. Description of the Related Art
An image projection apparatus is an apparatus for magnifying an image and projecting the magnified image onto a screen. As a typical example of the image projection apparatus, there is a projector. Previously, because the image projection apparatus has been used in displaying materials for presentation in certain places, such as a meeting room, a classroom, and so on, there was no need for a user to carry the image projection apparatus.
However, these days, portable multimedia apparatuses, such as a digital camera, a digital camcorder, a portable media player (PMP), a notebook PC, and a mobile phone, are widely used. As the applicability of such portable multimedia apparatuses has gotten higher, there has been a demand for conveniently sharing an image played by the portable multimedia apparatuses with other people anywhere. Accordingly, research for miniaturizing the image projection apparatus, such as the projector, is being carried out to enhance a portability and a mobility thereof.
As one of the parts of an image projection apparatus, there is a focus adjustment device. The focus adjustment device adjusts a focus of an image projected onto a screen. The portable image projection apparatus, which is used in various places, may require varying a distance between the portable image projection apparatus and the screen. In this case, a user can adjust the focus of the image projected onto the screen by moving a projection lens unit with the focus adjustment device. To fabricate the portable image projection apparatus, it is necessary to miniaturize the focus adjustment device.
However, as the focus adjustment device and the portable image projection apparatus are reduced in size, it is feared that the focus adjustment device may too sensitively react to user's operation. In other words, even though the user operates the focus adjustment device only a little, the projection lens unit may be excessively moved. In this case, it is difficult to stably adjust the focus of the image projected onto the screen. Accordingly, it is desirable that the excessive reaction of the focus adjustment device be suppressed.